P012 The administration of mm-miR-378a-3p exacerbates chronic inflammation and fibrosis in a murine intestinal model

Abstract

Abstract Background Fibrosis constitute an important complication of CD. MicroRNAs (miRNAs), which are small RNA molecules that regulate gene expression, have been shown to participate in the molecular interactions of both inflammation and fibrosis. Lower levels of miR-378a-3p have been reported associated to murine liver fibrosis (Hyun et al. DOI: 10.1038/ncomms10993) and we analyze here the relevance of miR-378a-3p on intestinal fibrosis. Methods B57BL/6 mice were intravenously injected with 2,5mg/kg of negative control (NC) or mm-miR-378a-3p mimic, twice a week and received vehicle or Dextran Sulfate Sodium (DSS) for 2 cycles (7 days drinking DSS 2% in water solution followed by 10 days drinking water). Body weight and DAI score was obtained every day and the colon was collected after sacrifice. Sirius and hematoxylin-eosin dyes were employed to determine the fibrosis and structural state in 5µm slides of intestinal tissue. Gene expression and miRNA profiles were analyzed by RT-qPCR. Human small intestinal fibroblasts (HSIF; P10760, Innoprot, Spain) were transfected with 20nM of NC or hsa-miR-378a-3p mimic during 24h. Results No significant changes in body weight, DAI score, and colon length were detected between mice receiving NC and those receiving mimic, all along the two DSS cycles. Colon of mice treated with DSS, exhibited a significant diminution in the mRNA expression of mm-miR-378a-3p compared with naïve samples. In DSS-treated mice, the iv administration of the mimic compared with the NC: a) significantly increased levels of miR-378a-3p in the colon; b) increased the number of neutrophils, and heightened changes in the glandular epithelia and architectural distortion (figure 1a) C) decreased the number of lymphoid follicles (figure 1a); d) slightly increased collagen deposition, as analyzed by sirius red (figure 1b) and e) significantly increased the mRNA expression of Tgfb1, Il1b, and Mmp2. Treatment of human intestinal fibroblasts with hsa-miR-378a-3p mimic did not significant modify the mRNA expression of markers of fibrosis but it significantly increased the mRNA expression of two antiapoptotic molecules BCL2 and MCL1. Conclusion Levels of mm-miR-378a-3p are diminished in a murine model of intestinal fibrosis; The exogenous administration of miR-378a-3p, increased the acute inflammatory response and the expression of fibrosis markers in murine fibrotic colon and the expression of antiapoptotic molecules in human intestinal fibroblasts.